Ok, so your pictures never look like a professional's do, and you want to know why, right?
Especially in digital, I think that the biggest thing that you pay for is how short the delay is between the time you push the button on the camera and when the shutter actually clicks, if that makes sense...you know, when you have a great moment, and you never get it on film? That's the cheapie mom camera. The delay is too long, and you end up taking a picture of someone elses kid picking his nose.
Another thing to look into is the lens size. It's cheaper to buy a Kit, where there's a camera and lens together, however, Most of the "Kit" lenses only stop down to 5.6, which is almost like a mom camera in depth of field. One of the reasons that a professional picture looks so different is that a lot of times the subject is sharp, but the background is blurred out. You can do that a little bit on the kit lenses, but in order to get a sharp subject and blurred background, it's really nice to be able to stop down to 2.8. That being said, a 70-200 2.8 lens with image stabilization is $1800 and a 5.6 one is about $200, so you can choose how important that feature really is to you ! ;) A lens with a 2.8 also helps alleviate all of those nasty black shadows that you get when you take a picture with a flash on camera...you're letting in more natural light, so you don't need as much flash.
As for an entry camera body, I'm a canon girl, so a canon rebel is ok, a canon 40 or 50 D is better, bigger screen on the back to view the pictures, more bells and whistles, but most importantly, shorter time between when you push the button and when you actually take the picture. Don't buy a digital camera used. You may think that you're getting a bargain, but digital cameras aren't made like film cameras...they are only made to assume a certain amount of "clicks", then they're through. So go buy that camera, take a lOT of pictures and Let me know what you think!